Detergent composition



July 5, 1955 v. MILLS ET AL 2,712,529

DETERGENT COMPOSITION Filed July 24, 1950 United States Patent C) DETERGENT COMPOSITION Victor Mills, Wyoming, and Hans B. Stromberg and Clilord B. Kemp, Cincinnati, Ohio, assignors to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Application July 24, 1950, Serial No. 175,516

Claims. (Cl. 252-138) This invention relates to a method of improving the physical characteristics and of minimizing defects of heatdried detergents containing effective proportions both of sodium triphosphate and of anionic synthetic detergents of the sulfated and/or sulfonated types, and to ,novel detergent products made by this method. This application is a continuation-in-part of Serial No. 55,656, led October 2l, 1948, now abandoned.

It is known that sodium triphosphate improves the cleansing performance of anionic synthetic detergents, and that when this phosphate is employed in amounts ranging from two to ve times the amount of the synthetic detergent an unusually effective washing and sudsing composition is obtained, one which is comparable in efficiency to good laundry soap in soft water and far superior to laundry soap in hard water.

Experience has shown, however, that the manufacture of triphosphate-synthetic detergent compositions in heatdried form is beset with difliculties such as balling, lumping, caking, and the formation of very slowly soluble sand-like triphosphate agglomerates, and it has also been found that phosphate detergent compositions have an undesirable tendency to corrode aluminum. Objects of the invention include the overcoming of these manufacturing diiiiculties, and the improvement of the physical characteristics of these products.

By incorporating sodium silicate in triphosphate-containing detergent compositions the tendency to corrotie aluminum is successfully controlled. This is not surpris-- ing because silicates have in the past been utilized in various alkaline compositions to check the corrosion of metals such as aluminum. lt has also been common practice to employ sodium silicates as builders in the formulation of soap compositions and synthetic detergent compositions, and we make no broad claim to invention in the incorporation of silicate in detergent compositions of the type with which we are here dealing.

The invention claimed herein is based on our discovery that unless critical limitations of composition and method of processing the compositions are observed the incorporation of silicate in these detergent compositions frequently causes new defects in the product which are much more objectionable than the defect sought to be overcome by the use of silicate, whereas by observing these critical limitations products are obtained which have totally unexpected advantages over otherwise similar silicate-free compositions.

Thus we have found that unless (l) the alkalinity, (2) the concentrations of certain of the ingredients in the detergent composition, and (3) the time that elapses between the addition of the silicate and spray drying of the detergent composition are suitably controlled the crutcher mix will not spray well, and Water solutions of the detergent product will be turbid or contain occulent precipitates, whereas following critical limitations we maintain the silicate Vin substantially fully solubilized form. v

The unexpected benefits which we have found to result when sodium silicate in suitable amount isv suitably incorporated in triphosphate-containing synthetic detergent compositions are related to former diiiiculties chiefly Patented July 5, 1955 attributable to the triphosphate component of the product, and especially to the natural fragility of spray dried detergent granules. Anhydrous sodium triphosphate occurs in two distinct crystalline forms or phases, known as Form I (formed at high temperature) and Form II (formed at lower temperature), which are readily distinguishable by X-ray diffraction analysis as well as by marked differences in their hydration behavior. Both yield an identical hydrate, namely the hexahydrate, NasPaOio 6H20.

Heat-dried and particularly spray-dried detergent compositions as a rule tend to be dusty (due to physical breakdown of too fragile granular particles) if overdried, and to cake and lump objectionably (due to agglutination of sticky granular particles) if under-dried. The dusty fines which occur in over-dried granular products are also objectionable in that they cause packing of the product so that it will not flow freely.

It has beenfound that the moisture range between this over-drying and under-drying is very narrow, and indeed is practically 'non-existent in some cases, when triphosphate-containing synthetic detergent compositions which contain no silicate are spray dried. We have found that the incorporation of sodium silicate (under suitable conditions and in suitable amounts) into the crutcher mix which is to be spray dried, not only widens the permissible moisture range between overand under-drying, a matter of considerable importance from the standpoint of manufacturing control, but also increases the physical strength or ruggedness of the individual granules to such an extent that their tendency to break down into dust is greatly reduced even as compared with the best product heretofore produced without benefit of silicate. The incorporation of silicate also results in the production of a free-flowing product having substantially no tendency to agglutinate or ball when added to water at the time of use by the consumer.

In the absence of silicate the aforementioned physical defects of spray dried granular products (fragility, dustiness, tendency to lump or cake in the package, and to ball 'when used) are prone to be particularly serious when Form Il triphosphate is a major component of the detergent composition, and our invention is therefore taining very incompletely hydrated Form 'Il triphosparticularly valuable in bringing about important improvements in products `of that composition. The importance of these improvements is the greater when it is understood that Form Il triphosphate is generally preferred over Form l because the latter hydrates with such rapidity when contacted with water, as for example when it is incorporated in aqueous detergent crutcher mixes, that it tends to form hard lumps (even under conditions of good agitation) which frequently persist through the entire processing and appear as hard sand-like particles in the final heat-dried product. In fact, this tendency to form slowly soluble, hard, sand-like particles is so marked that they are formed with triphosphates containing as little as 10% of the Form I variety when used in compositions that do not include silicate. We have found that by the use of silicate in its triphosphatedetergent compositions of this invention, triphosphates containing large amounts of the Form I variety can be incorporated with the aqueous detergents without forming these objectionable sand-like particles.

Form Il triphosphate, quite unlike Form I, hydrates very slowly, and unless prolonged time (several hours usually) is allowed for its hydration prior to spray drying the spray-dried synthetic detergent product containing this phosphate may have such bad caking or packing properties, due in part to hydration after spray drying, as to be unsalable. We have discovered that by proper use of silicate, as herein described, an otherwise identical composition may be spray dried from a mix conphates to yield a product virtually free of caking and packing tendencies, a product which is free flowing, substantially dustless, and essentially non-balling.

` Thus the use of silicate in accordance with our invention permits one to use, in conjunction withv sulfated and/or sulfonated detergents, the phosphate, i. e. triphosphate, which has been found to give outstanding performance from the standpoint of detergency and sudsing, While at the same time both avoiding defects and diculties which formerly accompanied its use, and also securing highly desirable physical characteristics much sought after inV spray Vdried detergents of any formula.

. The ability to make good spray dried detergent products containing Form II triphosphate which is only partially hydrated has a further advantage. The prolonged hydration period (aging in the crutcher) which would otherwise be required results in more or less reversion. By reversion we refer to a tendency of triphosphates to undergo an intramolecular absorption of water with the resultant formation of somewhat less alkaline salts of pyroand/or ortho-phosphoric acids. This reversion in general occurs only when the triphosphates are in water solutions or slurries lat high temperatures and/ or during dehydration of their hydrates. Such reversion Vdue to extended hydration periods we avoid almost completely when making these products by the present process, and this is advantageous not only in the saving of time and consequent simplification of manufacturing equipment, but also because the pyrophosphate and orthophosphate reversion products are distinctly infertior to triphosphate as builders sfor synthetic detergents. v

The spray dried triphosphate-containing synthetic detergent compositions of our invention are believed to be unique in that: they contain sodium silicate as anV effective corrosion inhibitor, this silicate is in substantially fully solubilized condition, the composition is outstand# ngly low in triphosphate reversion products, and the product is non-sticky, free-flowing, non-dusty, non-caking, and non-balling to a superior degree, as well as being free of undesirable hard sand-like triphosphate agglomerates. (We use the expression fully solubilized silicate in a broad sense, i. e. we refer to the silicate n the heat-dried product as having been maintained in such condition during the process that it dissolves in Water and/ or assumes a peptized colloidal state in water at'washing concentrations such that insoluble siliceous floc is not formed.) Y Y The term anionic synthetic detergent as employed hereinafter is used in a limited sense to denote watersoluble salts of sulfuric reaction products of alkyl and substituted alkyl compounds containing 8 to 18 carbon atoms in the alkyl group, characterized by their high solubility in Water, their resistance to precipitation by the mineral constituents of hard Water, and their surface active and effective detergent properties. Typical examples of such detergents are alkyl sulfates, alkyl aryl sulfonates (such as alkyl benzene sulfonates), mono-V glyceride sulfates and sulfonates, sulfoethyl oleates,rsulfo ethyl-N-methyl oleic amides, and the like. Numerous components one mayy also'incorporate other inorganicl builders such as alkali carbonatos, phosphates, borates, etc., organic builders, perfumes, preservatives, coloring matter, and other substances commonlyfound Vin detergent compositions; such further components may comprise as much as 50% Vby, weight, or'even more, of thedetergent compositions described herein. v Y

In the. accompanying drawings, which will serve to identify and diierentiate the phosphates with which We are principally concerned, f 'I Figures l to 4 represent X-ray diffraction patterns characteristic of four different phosphates as follows:

Figure 1, anhydrous sodium triphosphate in the phase known as Form I,

Figure 2, anhydrous sodium triphosphate in the phase known as Form Il,

Figure 3, sodium triphosphate hexahydrate, and

Figure 4,- anhydrons sodium pyrophosphate.

As is apparent from the drawings, the several X-ray diffraction patterns show differences in crystalline structure in the various phosphates represented. AThose rings n in the dilraction patterns which are particularly useful for identication of each phosphate are indicated by numerical values of the interplanar spacings in ngstrom units, corresponding to these rings. y

Other objects and advantages of the invention and theA manner of practicing the invention will be better understood from the following examples, in which all compo sitions are given in terms of percentages or parts by' weight.

Example I .-100 parts of Form Il anhydrous sodium triphosphate having a pH of 9.8 as measured in a 1% solution in Water at 25 C., were thoroughly mixed in a crutcher with an aqueous detergent mixture containing 36 parts of sodium alkyl sulfate prepared by sulfating the fatty alcohols obtained bythe reduction of coconut oil; and 26 parts of sodium sulfate. 27 parts of an aqueous'4 mixture of 38.8% NazO caustic soda and sodium silicate having an overall solids content of 44.5% and an overall SiOz/NazO ratio' of 1.8 were then added and the entire. mass was stirred continuously for one hour. The uid .mass, which Acontained about 40% water, was then promptly spray dried in well knonw manner, yielding a highly satisfactory rapidly dissolving detergent comprised of tough, free-flowing granules having a slightly glossyappearance; The product, which contained 7.5% mois-1 ture, showed no tendency to lump Vor'cake either during.

i packaging operations, storage or when dis-solved in water.

It gave clear solutions in water at washing concentra-- tions of about 0.5%. The pH of a 0,5% solution ofthe product was 10.1 at 25 C. Y p

In direct contrast, a product obtained by spray drying a like mixture of sodium triphosphateand the aqueoust alkyl sulfate mixture to which no silicate mixture (sili-n cate-l-caustic soda) had been added was sticky, fragileand lumped badly even though it contained only 4.5%4 water. The soft dull granules broke down readily toform much dust. A comparison of the dust content and? toughness of the two products is illustrated in Table Iv.. wherein the values for dust content were determined by measuring, with a photoelectric cell, the amount of light, passing through a closed chamber before and after pour ing a package of the product over a bathe in the chamber. 'Ille difference in the two measurements thus obtained, which is a measure of the amount` of light obscured bythe dust cloud formed, is thus proportional to the amountof dust suspended in theair. The arbitrary scale used,- for this measurement was such that a very dusty productV would lgive a value (i. e; a difference betweenthe twovl measurements) of about 100. Dust content values were'v read immediately after pouring the product (e. g. 47 in the case of the product containing no silicate).

Table I l s (Ai) "d i pdue Packed Product:`

Product f Through Through'` Dust l M- Dust 100 M Content screen Content screen" j l Y Percent Percent wlthoutsnicate 47 9.7 Y sr n.2 With silicate 20 5. l 29v From Table I it is apparent that not only did the silicate greatly reduce the dust content but it also greatly reduced the amount of hnes (line particles that would pass through a Tyler standard 100 mesh screen). The toughness imparted to the granules by the silicate is further illustrated by the fact that the non-silicated product after spray drying (see column A) broke down considerably in passing rthrough the conveying, storage, and packing operations with marked increases in dust and fines content (see column B), whereas the packed silicated product was not nearly as dusty, after all the above mentioned operations, as the initial non-silicated product.

The time that elapses between the addition of silicate to the aqueous mix and spray drying is also important in the manufacture of the silicated products described in this invention. A portion of the above mixture was allowed to stand for four hours before spray drying. Great dihiculty was experienced in spray drying and pumping this aged mixture. The aging presumably allowed a gelatinous form of silicic acid or silica gel to form (that had the appearance and feel of hydrated tapioca) which prevented proper atomization. This gel also frequently clogged the strainers and pump valves, completely halting the pumping'op'erations. The product obtained under these conditions was 'not of good quality. It was soft, sticky and often dusty. It was also noted that solutions at washing concentrations 'of this spray dried aged material developed ilocculent precipitates.

In the production of products as described in Example 1 we have maintained the pH of the product at or above pH (measured on a 0.5% solution at 25 C.) by using a 1.8 SiOz/NazO ratio silicate. This degree of alkalinity, coupled with prompt spray drying, was used to avoid the formation of gels and precipitation of iiocculent siliceous materials in washing concentrations.

Silicates can be further solubilized by the proper selection of the synthetic detergent used. Thus valkyl benzene sulfonates are more effective than the alkyl sulfates, and permit the production of compositions which produce floe-free solutions having lower alkalinity as vshown in the next example.

Example 2.-l00 parts of Form Il anhydrous sodium triphosphate, having a pH of 9.6 as measured in a 1% solution in water at C., were thoroughly mixed in a crutcher with an aqueous detergent mixture containing 36 parts oi" sodium alkyl benzene sulfonate, and 44 parts of sodium sulfate. A sodium silicate solution containing 13 parts of silicate solids having a SiO2/Na20 ratio of l2.6 were 'then added and the 'entire crutched mass was stirred continuously for 90 minutes. The crutched mass, which contained about 40% Water, was then spray dried in well known manner yielding a highly satisfactory rapidly dissolving detergent composed of tough, free-owin'g, non-dusty granules having a slightly glossy appearance. The product, which contained 9.75% moisture, showed no tendency to lump or carie either during storage, packaging operations or when dissolved in water. This product was outstanding in that it showed a zero dust count and had a very tough granule that resisted breakdown surprisingly. It showed a zero dust content both before and after packaging.

This product differs from that of Example 1 not only in its somewhat superior physical properties but in the silicate solubilin'ng eiect obtained vby 'the use of sodium alkyl benzene sulfonate which permits the use of lower alkalinity in the product. This product dissolves in Water at washing concentrations without the formation of any insoluble doc even though its pH in a 0.5% solution at 25 C. is only 9.7. Indeed, excellent products have Vbeen obtained 'with pH's as low as 9.5 Without the formation of insoluble lloc; however, in some instances as the pH drops below 9.5 the granules become less tough and have a slight tendency to lump and cake. when prepared as described above, and a pH of at least 9.5 is preferredV for this reason. Y

The time of mixing of the detergent-phosphate'- silicate mix is here again of importance as in Example l. We have found that when operating in a pH range of 9.5 or over (as measured in a 0.5% solution of the spray dried product) the time that elapses between the addition of the silicate and the spray drying should in general not exceed 3 hours. While much good product has been produced while operating close to the 3 hour limit and in some instances even over 3 hours when operating at a high pH, we prefer to operate below this limit so as to avoid the formation 'of large tapioca type gelatinous particles that give so much trouble in pumping and spray drying.

In the above examples as well as other examples, detergents of each of the various types referred to in defining the term or mixtures thereof may be substituted for the detergents specifically mentioned in the examples with good results. When this is done, one may wish to make obvious adjustments of the proportions of the constituents to take care of any differences in inert ingredient content, or diiferences in silicate solubilizing properties.

In the above examples there was a reduction of alkalinity during the drying process. This can be accounted for partially by the formation of more acid phosphates due to some reversion of the triphosphate. Knowing that the pt-I of the mixture will drop, we add suliicient alkaline material to allow .for a normal drop of about 0.2 pH during the drying process.

The products of the present invention and the methods used lfor processing them have a distinct advantage over the previous production of detergent compositions comprising triphosphates and Form il triphosphates in particular. Silicated products typical of the above examples can be produced with the excellent physical properties previously cited over a wide moisture range of approx mately 3 to10 per cent, and often as high as 13 per cent. Similar products made without the benefit of the silicate usually had to be aged in the crutcher for about 4 to 8 hours to permit the slowly hydrating Form Il triphosphate to become completely hydrated. In this manner products of relatively high moisture content (about 8 to 9 per cent) could be made, but at the expense of some loss in detergency due to reversion of the triphosphate not only during the aging period in the crutcher but also during heat drying. Reversion during the aging sometimes would run as high as 10 per cent or more of the original triphosphate according to the hydration time permitted, and since part of the fully hydrated triphosphate (e. g. NaslsOio-HzO) would also revert during the heat drying, the total reversion might run 2() per cent or more. Silicate as used in the present invention entirely eliminates the need of prolonged aging of the crutcher mix containing Form II triphosphate and permits the drying to proceed while the phosphate is still largely in the anhydrous form. It thus reduces the amount 0i triphosphate reversion which otherwise occurs in the crutcher and during drying, a fact borne out by analyses of detergent compositions prepared according to the methods taught in this invention.

The silicated products produced by the present process have a marked avidity and/or capacity on the part of the silicate for water. Thus nonsilicated products of the above mentioned type containing 50 per cent Form II sodium triphosphate and made without prolonged hydration before spray drying feel damp if their water content exceeds approximately 3 per cent. The same product but with 4 to 7 per cent silicate solids added as prescribed in this invention generally contains 8 to l0 per cent water and yet feels dry even though usually less than half of the water present can be accounted for as triphosphate hexahydrate. Likewise during storage of the dried product the silicate apparently will absorb water without allowing the product to lump, as

it doesl Without silicate. In general, we prefer a finished product such that not more than about 50 per cent of the triphosphate is in the hexahydrate form. Other advantages of the silicated product, as previously noted, are: 1) the increase in productive capacity of the equipment with the decrease in aging time required, and (2) a marked reduction in the tendency of the detergent to corrode aluminum. The addition of 4 to 7 per cent'silicate solids by weight on a finished product basis has been found to be sutiicient to accomplish not only the reduction in corrosion desired by alsok to improve the physical properties. When operating at lower pHs (i. e. below a range of 10 to 10.3) it is frequently desirable to use not more than 7 per cent silicate solids in order that the silicate may be maintained in a peptized or solubilized form, and the hydration time is controlled accordingly. However, Example 3, shown below, illustrates a case where large amounts of silicate were Vmaintained in a solubilized form by using alkyl benzene sulfonate entirely for the synthetic detergent and also maintaining a high pH.

Example 3.-7-232 parts of sodium silicate solids, in the form of a water solution containing 14.8 per cent NazO and 29.6 per cent SiO?. were mixed in a crutcher with an aqueous detergent fluid containing 62.4 parts of sodium alkyl benzene sulfonate. 19 parts of a Form II anhydrous sodium triphosphate having a pH of 9.6 as measured in a 1% solution at 25 C. were stirred into the crutcher'mass and thoroughly agitated for about one hour, and then promptly spray dried in well known manner. A free-owing, dustless product having an apparent density of 0.16 gm./cc. was obtained. It had a moisture content of 3.9% and a pH of 10.0 as measured in a 0.5 water solution at 25 C. It showed a good resistance to lumping and caking. It produced only a faint trace of insoluble oc in a 0.5% solution in water. This product which contained 42 per cent active synthetic detergent, 12.3 per cent triphosphate and l5 per cent sodium silicate compares with the preceding examples as follows.

Parts Parts Parts Triphos- Synthetic phate Detergent .silicate Preeeding Examples 1.0 0.3 i 0.1 Example 1.0 3.4 1:2

With regard to physical properties, the products, in the preceding examples may be slightly superior to the product shown in Example 3 but the latter is still an ontstandingly good product. Instead, products having excellent physical and solution properties may be prepared using proportions in the range of one part of triphosphate,

0.2 to 4.0 parts of active detergent and 0;07 to 1.2 parts of silicate solids, the amount by Vweight of silicate solids in theV nished composition being in the range of 4 to 25 per cent, and the amount of synthetic detergents and' triphosphate totalling at least 25 per cent. Y

In Example 3 advantage was also taken of the large amount of silicate used in that it was added to the detergentrbefore addingthetriphosphate. In so doing the unbu'ered detergent solution quickly assumed the pH of the silicate, which is about 11.7 at that concentration. This procedure, with thorough mixing of the mass as the triphosphate was added thereafter, kept the silicate solution in a higher pH range throughout the operation than if the phosphate had been added irst, thereby avoiding a pH range wherein gel or lloc formation would proceed rapidly.

The Form Il triphosphate employed in the practice of this invention need not be a pure salt.l Indeed, we have used commercial materials, with good results, lcontaining substantial amounts o f Form l triphosphate, pyroand/ or amorphous phosphates. However, we prefer to employ triphosphate of high Form ll content 18 to avoid (l) the lumping tendency of Form I and the pyroand amorphous phosphates often found with it, (2) the marked dustiness often obtained with pyrophosphate, and (3) the extreme hygroscopicity often obtained with the metaphosphates. Mechanical mixtures of other phosphates together with triphosphates, e. g.

pyro, ortho-, rmeta, and tetraphosphates, may be used in the practice of the invention. In adjusting the pH of the mixture it should be noted that the trisodium orthophosphate has a high pH of about 12.0 (as measured at C. in 1% water solution)y whereas the pHs of tetrasodium pyrophosphate and pentasodium triphosphate.l normally approximate 10.1 and 9.7 respectively. The pyrophosphate shows a slight but negligible tendency to revert to the orthophosphate form. If metaor the in termediate polyphosphates are used, which have VpHs approximating neutrality and higher respectively, much greater reversion may be experienced, and unless com pensated for by the use of alkalizing materials much of the silicate may be precipitated as lloc. However, with proper adjustment of the pH, Vso as to enable the silicate to stay in solution or colloidal suspension these other phosphates, along with triphosphate, can often be employed to good advantage in the present invention.

Our preferred range of Form I content in the triphosphate runs from a minimum of about 5% to a maximum of about to 40%. The following example illustrates the use of a triphosphate in this range. Example 4.-50 parts of a commercial grade of anhydrous sodium triphosphate, comprising 70% Form Il, and 25% Form I triphosphate and 4% pyrophosphate, and having a pH of 9.8 as measured in a 1% solution inI water at 25 C. were thoroughly mixed in a crutclier.y

with an aqueous detergent mixture containing 11 parts of sodium alkyl sulfate prepared by sulfating the fatty'r alcohols obtained by the reduction of coconut oil, 13 parts of sodium sulfate, and 7 parts of sodium alkyl benzene sulfonate. A sodium silicate solution contain-I ing 7 parts of silicate solids having a SiO2/Na20 ratiov4 of 2.4 were then added and the batch was stirred continuously for approximately minutes. The crutched mass, which contained about water, was thenrspray dn'ed in well knownvmanner yielding a highly satisfactory, rapid dissolving detergent composed of tough, free-l flowing, non-dusty granules having a slightly glossy appearance. The product, which contained 10.2% moisture, showed no tendency to lump or ca ke either during storage, packaging operations, or when dissolved in water. f' *Thisl product resisted breakdown very well and after packing had an average dust count of about 3. It'had a pH of 9.8 as measured in a 0.5 water solution at 25 C. It produced only a very slight amount of insoluble siliceous-hoc in a 1.0% solution in water. j

Triphosphates having Form Icontents above the preferred range of 5% to 40% can be used with satisfactory results in detergent compositions when suiicient silicate is added to prevent triphosphate agglomeration. We prefer to use amounts of silicate such that the triphosphate agglomeration is so repressed that the 'agglomerates formed are of such small size that they are cornpletely dissolved or are reduced in less than a minute to a size so small as not to be objectionable to the housewife using the product. i

Some detergents prepared from higher molecular weight organic compounds have a tendency to produce p Except for such detergent Y armeno 9 irritating to hands. As the pH of the product is `lowered (e. g. to 9.0 pH) we iind the time that elapses between the admixture of silicate and heat drying should preferably be greatly reduced if floc formation is to be avoided.

Studies made with aqueous solutions of sodium silicatesodium triphosphate mixtures indicate that there is an iso-electric point in the neighborhood of 9.0 to 9.3 pH, i. e. the time during which no gelling of the aqueous mixture occurs appears to again increase as the pH drops below the value of approximately 9.0 to 9.3. Thus as the pH range of 9.0 to 9.3 is approached necessitating the shortening of the time that elapses between the addition of the silicate and spray drying, it becomes desirable to use continuous rather than batch mixing to avoid excessive gelling or oc formation. As the mixing time is decreased, triphosphates having high Form I contents can be used to advantage because of their shorter hydration time.

The desirability of such reduction in time is further indicated by a study of the effect of silicate concentration. It has been observed that in aqueous compositions at a pH of 10, containing 30 per cent sodium triphosphate and sodium silicate equivalent to 1.8 to 2.4 per cent SiOz, gelling began to be noticeable in about 2 minutes, whereas at 1.2 per cent SiOz the time for this to occur was 5 to 6 minutes. As the SiOz concentration was lowored below 1.2 per cent the critical time increased rapidly until at 0.3 per cent this time increased to about 20 minutes.

As the pH was lowered this critical time interval became progressively smaller until at a pH of 9.0 the critical time had dropped to about 15 to 30 seconds at an SiOz concentration of 1.8 to 2.4 per cent. Typical of chemical reactions in general, the reaction rate here also varies with temperature.

It is obvious that as variations are made in the detergent mix, such as pH, temperature, proportion of ingredients, degree of dilution with water, type of synthetic detergent, type of phosphate and other builders used, each specific combination of materials and conditions will call for an appropriate choice of a mixing time below which precipitation of oc may be avoided or kept at an acceptable Each case also calls for an appropriate choice of order of addition of the ingredients so that the time may be kept at a minimum during which the mixture passes through or exists under conditions that are particularly conducive to precipitation of oc. n

This invention is particularly concerned with detergent products consisting of particles in nely divided form wherein each particle contains the essential ingredients dealt with in substantially uniform mixture. nds its greatest usefulness in the manufacture of spray dried detergent compositions it is not limited to spray drying but is applicable to other heat drying processes, as in drum drying or heat drying or flaked products.

It is to be understood that the foregoing more porticularly described processes are to be considered as illustrative of the preferred method only; such changes and modifications therein are contemplated as would normally occur to those skilled in the art to which the invention relates.

In the appended claims all compositions are given in terms of percentages or parts by weight.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. In the process of manufacturing spray dried detergent compositions, the steps which comprise: (1) Incorporating l part of normal sodium triphosphate, containing at least about 60% Form Ii and not more than 40% nor less than 5% Form l in a uid aqueous mixture, together with 0.2 to 4.0 parts of non-soap anionic synthetic detergent of the group consisting of water-soluble salts of sulfuric reaction products or" alkyl and substituted alkyl compounds containing 8 to 18 carbon atoms in the alkyl group and mixtures thereof, characterized by their high Solubility in Water, their resistance to precipitation by While it mineral constituents of hard water and their surface 'active and effective detergent properties and 0.07 to 1;2 parts of sodium silicate, the proportions of said ingredients being so chosen that the spray dried product contains not less than about 4% nor more than about 25% of solubilized silicate solids and not less than about 25% total of synthetic detergent and tripolyphosphate; (2) maintaining the alkalinity of the duid mixture from the time silicate is incorporated therein at a silicate solubilizing pH not below 9.5 (as measured in an 0.5% solution in water at 25 C); and (3) spray drying the aqueous mixture within less than 3 hours after the silicate is incorporated therein and before gelation of the silicate occurs as is manifested by the appearance of tapiocalike particles in the aqueous mixture; thereby producing a spray dried granular detergent composition having particles of greatly improved resistance to physical breakdown and of outstanding freedom from stickiness, dustiness, and caking and balling properties as compared with otherwise identical spray dried granular compositions not containing solubilized silicate, and having the further properties of forming aqueous washing solutions substantially free of silicious floc and sand-like triphosphate agglomerates.

2. The process of claim 1 wherein the anionic synthetic detergent is a mixture of sodium alkyl sulfates and alkyl aryl sulfonates containing 8 to 18 carbon atoms in the alkyl group.

3. The process of claim 2 wherein the spray dried composition contains from 4 to 7% of solubilized silicate solids.

4. A spray-dried detergent composition in granular form having particles of greatly improved resistance to breakdown, and having an outstanding freedom from dustiness, stickiness, caking and balling properties, as compared to like heat-dried compositions that do not contain the hereinafter mentioned solubilized silicate, and having the property of forming solutions substantially free of silicious floc and sand-like triphosphate agglomerates in water at washing concentrations, comprised essentially of one part of sodium triphosphate derived from an anhydrous triphosphate comprising at least about 60% Form Il and not more than 40% nor less than 5% Form l, 0.2 to 4.0 parts of non-soap anionic synthetic detergent of the group consisting of water-soluble salts of sulfuric reaction products of alkyl and substituted alkyl compounds containing 8 to 18 carbon atoms in the alkyl group and mixtures thereof, characterized by their high solubility in water, their resistance to precipitation by mineral constituents of hard Water and their surface active and effective detergent properties, and 0.07 to 1.2 parts of solubilized sodium silicate, said composition having a pH of at least 9.5 as measured in a 0.5 per cent solution in Water at 25 C., said composition containing not less than about 4 per cent nor more than about 25 per cent of solubilized silicate solids and not less than 25 per cent total of synthetic detergent and triphosphate said composition having been spray dried within less than 3 hours after the silicate was incorporated with the triphosphate-containing mixture.

5. The product in claim 4 wherein the spray-dried composition contains from 4 to 7 per cent sodium silicate, and the anionic synthetic detergent is a mixture of sodium alkyl sulfates and sodium alkyl aryl sulfonates containing from 8 to 18 carbon atoms in the alkyl group.

References Cited in the le of this patent UNITED STATES PATENTS 1,912,175 Blough May 30, 1933 2,247,741 Beller July 1, 1941 2,333,443 Robinson Nov. 2, 1943 2,333,444 Robinson Nov. 2, 1943 (Other re erences en foiiowing page) 1 1 UNITED STATES PATENTS l A McGhie Feb. 5, 1946 Lind n n--- Mar. 12, 1946 King Apr. 15, y1947 Robinson June 21,V 1949 Strain Nov. 1, 1949 Waldeck July 18, 1950 12 2,115,880y AMacMlahon.l 11113118-, 195g FOREIGN PATENTS 690,352 France Sept. 19, 193() v OTHER REFERENCES f -Watz e1:Ar'tic1e in Die Chemie 55, pp. 356-359, 1942.* 

4. A SPRAY-DRIED DETERGENT COMPOSITION IN GRANULAR FORM HAVING PARTICLES OF GREATLY IMPROVED RESISTANCE TO BREAKDOWN, AND HAVING AN OUTSTANDING FREEDOM FROM DUSTINESS, STICKINESS, CAKING AND BALLING PROPERTIES, AS COMPARED TO LIKE HEAT-DRIED COMPOSITIONS THAT DO NOT CONTAIN THE HEREINAFTER MENTIONED SOLUBILIZED SILICATE, AND HAVING THE PROPERTY OF FORMING SOLUTIONS SUBSTANTIALLY FREE OF SILICIOUS FLOC AND "SAND-LIKE" TRIPHOSPHATE AGGLOMERATES IN WATER AT WASHING CONCENTRATIONS, COMPRISED ESSENTIALLY OF ONE PART OF SODIUM TRIPHOSPHATE DERIVED FROM AN ANHYDROUS TRIPHOSPHATE COMPRISING AT LEAST ABOUT 60% FORM II AND NOT MORE THAN 40% NOR LESS THAN 5% FORM I, 0.2 TO 4.0 PARTS OF NON-SOAP ANIONIC SYNTHETIC DETERGENT OF THE GROUP CONSISTING OF WATER-SOLUBLE SALTS OF SULFURIC REACTION PRODUCTS OF ALKYL AND SUBSTITUTED ALKYL COMPOUNDS CONTAINING 8 TO 18 CARBON ATOMS IN THE ALKYL GROUP AND MIXTURES THEREOF, CHARACTERIZED BY THEIR HIGH SOLUBILITY IN WATER, THEIR RESISTANCE TO PRECIPITATION BY MINERAL CONSTITUENTS OF HARD WATER AND THEIR SURFACE ACTIVE AND EFFECTIVE DETERGENT PROPERTIES, AND 0.07 TO 1.2 PARTS OF SOLUBILIZED SODIUM SILICATE, SAID COMPOSITION HAVING A PH OF AT LEAST 9.5 AS MEASURED IN A 0.5 PER CENT SOLUTION IN WATER AT 25* C., SAID COMPOSITION CONTAINING NOT LESS THAN ABOUT 4 PER CENT NOR MORE THAN ABOUT 25 PERCENT OF SOLUBILIZED SILICATE SOLIDS AND NOT LESS THAN 25 PER CENT TOTAL OF SYNTHETIC DETERGENT AND TRIOPHOSPHATE SAID COMPOSITION HAVING BEEN SPRAY DRIED WITHIN LESS THAN 3 HOURS AFTER THE SILICATE WAS INCORPORATED WITH THE TRIPHOSPHATE-CONTAINING MIXTURE. 